1. Field of the Invention
The present invention relates to air conditioning apparatus and method of operation.
Although the present invention is suitable for single compressor air conditioning systems having one or more stages, it is particularly advantageous for systems using tandem compressors and will be described in connection therewith. The term "air conditioning", when used herein is meant to include both the heating as well as the cooling of air in communication with an indoor coil of the heating/cooling system.
2. Description of Related Art
An air conditioning or heating system typically includes either a single or a multi-stage compressor. The capacity of a system using a multi-stage compressor is increased by increasing the compressor speed. Such compressors are generally equipped with a crankcase heater which turns "off" when the compressor turns "on" and turns "on" when the compressor turns "off."
In conventional systems using single speed compressors, the crankcase heater is "on" when the compressor is "off."
In many conventional systems using two-speed compressors, it is common to turn on the crankcase heater only when the ambient temperature is below 75.degree. F. One of the possible drawbacks to this kind of a system is that the outdoor ambient temperature may be above 75.degree. F. and the compressor may be off. If the crankcase heater system is not running, the refrigerant may be in a liquid state at that point of time and the two-speed compressor may be required to start up full of liquid and slugging. Since compressors are designed to handle gas only, such slugging is detrimental to the life of the compressor.
Conventional systems are subject to short cycling; that is, the compressor starts and stops frequently in response to the operation of a thermostat in order to maintain a fairly constant comfortable temperature. The short cycling of a compressor shortens its life considerably, and prevents adequate removal of moisture from the air. In addition short cycling of the compressor causes the turning on and off of the crankcase heater between cycles at frequent intervals, thus using an inordinate amount of power.
In a system with a single stage compressor, the indoor air handler may deliver the air flow at a variable rate depending on the difference between the outdoor and indoor temperature. In a multi-stage system, the air flow may be increased when the thermostat calls for an increased speed of the compressor. This, particularly in combination with a short cycle time, reduces the capability of a single stage or two stage system to remove moisture from the air being conditioned.
In light of the foregoing, there is a need for an air conditioning system and method that significantly reduces operating costs, provides superior home comfort, a higher SEER efficiency, and a longer trouble-free life.